MELBOURNE, Australia -- Serena Williams saved some family pride Wednesday at the Australian Open.

After her older sister Venus' upset loss to China's Li Na in the previous match on Rod Laver Arena, four-time champion Serena was down a set and 4-0 in the second before she rebounded for a 4-6, 7-6 (4), 6-2 win over Victoria Azarenka of Belarus.

Novak Djokovic played Jo-Wilfried Tsonga, the man he beat for the 2008 Australian Open title, in a later quarterfinal Tuesday. Andy Murray and Marin Cilic are already through to the semis from the other half of the draw.

"I've played him many times before, and I know he goes through ... some rock-solid phases at times," Federer said. "I just tried to stay positive."

Federer's victory snapped Davydenko's 13-match winning streak after the Russian player won the season-ending ATP World Finals in November at London and his 20th career title in Doha earlier this month.

Venus Williams couldn't make it to an expected sister semifinal, losing in a mistake-filled match featuring in a combined 110 unforced errors against Li.

The result is that Serena will take on Li, who beat Venus 2-6, 7-6 (4), 7-5. Justine Henin, playing in her first Grand Slam tournament in two years after coming back from a two-year retirement, will play Zheng Jie in the other semifinal.

Serena Williams was far from confident after the first hour of the match, thinking of her sister's loss.

"It was obviously on my mind," Serena said of Venus' defeat. "I saw maybe one or two points, maybe three. I don't want to watch too much, I get too nervous watching. Obviously I was incredibly disappointed."

So she started off tentatively.

" I wasn't playing my best, especially in the first two sets," she said. "I was down the whole match from the first point until the end. I wasn't surprised but I was definitely shocked."

Instead of wilting, she fought back from her big deficit in the second set with two service breaks of her own, easily won the tiebreaker and dominated the third.

"I think it's impressive the way she does it," Azarenka said. "She's a strong girl. She has very powerful shots."

Li and Zheng were the first Chinese pair to reach the quarterfinals at the same Grand Slam. Add semifinals now, and could the final be possible?

Serena Williams and Henin, with a combined 18 Grand Slam singles title between them (Serena 11, Henin 7) would seem to have the inside edge. But Li, who lost the first set and was twice down breaks in the second, says anything can happen.

"In China, we say if you have tough time and then you return back, maybe have good luck," Li said.

Venus Williams had more mistakes than luck against Li, who called the win the "best day of my life" and said she might celebrate with a beer Wednesday night.

"It's important to put the ball in the court," said Venus Williams, who served for the match in the second set. "I felt like sometimes I made some errors."

That was an understatement. The pair's unforced error went over the 100 mark midway through the final set. There were eight breaks of serve in the first 10 games of the third set.

"Unfortunately I let my errors creep in, and then I allowed her to dictate too much," Williams said. "But she played really well."

Azarenka wilted in her quarterfinal with Serena here last year, retiring in the second set with a virus after taking the first set.

This time, the 20-year-old Belarussian was undone by a trademark comeback by Williams, who is the only player to save match points on the way to three Grand Slam titles. She did it at Wimbledon last year and at the 2003 and 2005 Australian Opens.

Initially, Azarenka looked like she'd continue the Williams family woes. She broke Serena in the opening game and then, after fending off three break points, held her own opening serve in a game that lasted more than 15 minutes and went to deuce nine times.

It was mostly one-way until Williams started her comeback in the second -- winning five straight games and then getting on top again at the end of the tiebreaker. She dominated the third set, converting both her break-point chances.

Li, who is forecast to go into the WTA's top 10 rankings after the tournament ends, was dominant in the third set when it counted against Venus Williams, who has five Wimbledon titles and two at the U.S. Open.

"I don't like losing at all," Williams said. "No one does. I put in a lot of hard work to come out here and get a win (I'm) not at all pleased."

She didn't take kindly to suggestions that grass might be her only Grand Slam title option in the future.

"Like I said so many times before, if I would have, kind of gotten involved in what people said I would have never left the ghetto," Williams said. "So here I am playing pro tennis, playing well. The sky's the limit in this sport. I'm looking for that."